Vitamin D deficiency is a condition that happens when a person isn't getting enough vitamin D, which is needed for strong bones and overall health.

More to Know

Vitamin D plays a key role in bone health by helping the body absorb calcium and phosphorous, two of the basic building blocks of bone. We get vitamin D from the food we eat, and our bodies also make it when our skin is exposed to the sun. Without enough vitamin D, bones can grow too slowly and become soft, weak, or deformed.

Besides aiding bone health, vitamin D supports the brain, muscles, and immune system. It helps the body make new cells and fight off infection. It also reduces inflammation.

Vitamin D deficiency can occur in people who don't get enough vitamin D in their diet, have limited exposure to sunlight, have kidney or liver disease, are obese, or have conditions or take medicines that prevent their bodies from absorbing enough vitamin D. Vitamin D deficiency is more common in people who don't eat or drink dairy foods.

Keep in Mind

Doctors usually diagnose vitamin D deficiency by measuring levels of the vitamin in the blood. Other blood tests and X-rays to look for bone problems also might be done.

Treatment includes vitamin D supplements to raise the body's levels to normal, which helps to prevent or reverse bone problems. Some people also take calcium and/or phosphorous supplements. A healthy diet and careful sun exposure also can help.

All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts.